Film driving apparatus



Aug 1933? c. 1 H-ElsLl-:R' 1,926,789

FILM DRIVING APPARATUS Filed Dec. 28. 1929 I ChoPLes LHeLeLer, 2 bg HLSAttorney.

Patented ug. i, 1933.

1,920,783; MLM nnrvmo srraaa'rns Charles l.. liieisler, Schenectady, N.

Y., assigner to General Electric Gompany, a Corporation ci New YorkApplication December 28, 1929.v Serial No. 417,212

7 Claims.

My invention relates to apparatus for recording sound on a nlm or forreproducing sound from a record film. More particularly it relates tothat part of the apparatus by which the lm is driven past the point atwhich the record is made on or at which the record is read of the film.It is the object of my invention toprovide apparatus of this characterhaving improved means for driving the lm with the desired degree ofuniformity past the'point of recording or of reproduction.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims;

Referring to the drawing, Fig. 1 is a side View partly in section ofapparatus involving my invention; Fig. 2 is a cross-sectional view ofthesame taken on the line 2-2 of Fig. 1; and Fig. 3 is a fragmentaryview corresponding to Fig. 2 showing a modification.

While my invention is applicable both to apparatus for recording soundon a nlm and to apparatus for reproducing sound from a lm record.- Ihave chosen for convenience to illustrate it as forming a part of areproducing apparatus.

The film 1 having the sound record 2 thereon adjacent to one row ofsprocket holes is shownl engaging opposite sides of the same sprocket 3,suitable pressure rolls 4 and 5 being provided to hold the lm againstthe sprocket. Ob* viously separate sprockets may be employed if desiredto engage the lm-as it approaches and leaves the apparatus and they maybe variously positioned in accordance with the desired path of the filmthrough the apparatus. From the pressure roll 4 the film passessuccessively in a tension loop over the control roll 6, over the 40combined pressure and guide roll '7, around the drum 8, over thepressure roll 9, and thence in a free loop to the pressure roll 5 andsprocket 3. Both the sprocket and drum are driven from a common sourceof power such for example as a synchronous motor and where gearing isemployed between the source and the drum, I prefer to have a ywheelsecured to the shaft 10 of the drum.` The drum shaft is journaled inbearings one of which is shown at12 and inthe form illustrated the drumcomprises the two coaxial portions 14 and 15, portion 14 being integralwith the shaft 10 and portion 15 being detachably secured by the thumbscrew 16 to the reduced extension 17 of the shaft. Within the drum isthe 'xed member 19 which supports the photoelectric cell 20 and itselfis supported by the bar 21 extending out through the annular gap betweenthe two drum sections. By meansof the optical system shown at` 22 lightfrom a suitable source is focused on the record portion of the film inthe form of a narrow transverse band or line, the light after beingmodulated by the sound record passing on into the photo-electric cell.If desired, the drum may comprise but the one portionr 14, that 'part ofthe lm bearing 65 the sound record overhanging the end of the drum.

As has already been mentioned above, the sprocket and drum are connectedto be driven m from the same source, preferably a synchronous motor, andif this driving connection is such that the sprocket and drum .rotatewith a xed ratio relative to each other it is found in practice that theloop or the amount lof slack film between the sprocket and drum willeither grow steadily larger 1 as the machine is operated or will growsteadily smaller, the nlm eventually becoming taut and being damaged.This is .primarily due to variations in film shrinkage. I have overcomethis diiculty by providing aj compensator 23 which is 80 shown arrangedin the drive connection to the drum, the effect of 'which isI to soregulate the speed of the drum that it moves the lm at exactlythe samespeed as does the sprocket. The compensator comprises essentially adifferential S5' mechanism by means of which the movement of the wormwheel 24 driven by' the worm 25 on the motor shaft rotates the drumshaft 1G at a variable speed depending upon the pressure of the brake 26on the brake wheel 27. Through gear D0 24a and other gears, not shown,movement is transmitted from gear 24 to sprocket 3. Brake 26 is mountedon the lever 28 to which the spring 29 is attached to'apply the brake.Engaging the lever 28 is the roller 30 on the arm 31 secured to 9b shaft32 to which also is secured lever 33 carrying roll 6. The details of thecompensator construction form no part of my present invention and aredisclosed' and claimed in various' forms in my Patents 1,771,922, July29, 193.0 andx1,793.'99, 10U Feb. 17, 1931 andin my copendingapplications Serial No. 212,349 filed August 11, 1927, and SerialNo.'34l,147 filed Feb. 19,` 1929 all of which are assigned tothe sameassignee as the present ap` plication. Heretofore I have applied.aspring to the lever 33 to yieldingly hold the roll 6 against the filmloop. Such a spring is shown at 25 in my above-mentioned' Patent1,771,922. In my present construction I have dispensed with the springand instead have applied the mass 35 to 110 the lever. By reason of itsweight this mass causes f the lever 33 in response to an increase insize A ing themselves of the film loop to rotate counterclockwisekeeping the desired tension in the film approaching the drumandoperating the brake lever 28 to ,f release the brake against thetension of the spring 29. In addition to the above functions which alsowere performed by the spring formerly employed, the mass 35 functions asan inertia device to further steady the movement of the film. Because ofthe mass 35 the lever 33 is less responsive to small variations in thespeed of the film as feci by the sprocket such as may come fromimperfect sprocket tooth action or from the gearing employed in thedrive connection to the sprocket, hence the brake 26 which regulates thespeed of the drum and consequently the film speed is less subject tothose Variations than inthe former construction.` I prefer that thetorque produced by the mass 35 be sufficient only to operate the brakelever against the spring 29 and to cause the roll 6 to exert a lightpressure against the lm loop so as to follow any gradual changes thattake place in the size of the loop. When such a machine is first startedafter being threaded with a film the lever 33 slowly moves one wayor theother for a few seconds while the parts are adjustand then appears toremain fixed during the passage of the remainder of the film.

Roll '7 mounted on arm 38 is a combined pressure roll to press the lmagainst the drum and a guide roll having end flanges which by engagingopposite edges of theA film prevent side weave thereof. Where the filmleaves the drum it passes over the pressure roll 9 and into a free loopbefore reaching the pressure roll 5 and sprocket 3. It has been foundthat where a film is wrapped about a power actuated drum and is `pressedthereagainst bya roll which is caused to rotate through its contact withthe film on the drum as in the present case, there is a tendency for theroll to retard the film with the result that there occurs a backwardcreepage of the film on the drum. For the proper recording andreproduction of sound, the rotation of the drum should be uniform to ahigh degree of precision and the film should follow the drum with a likedegree of` precision. vAny creepage that occurs means that the film isslipping over the surface of the drum and this slippage is not as asteady movement but is of a rapid intermittent character. Such departurefrom the highly uniform movement of the drum obviously offsets to acertain extent the advantages of moving the film by the drum. Moreoverit is found that when two spaced pressure rolls are employed to pressthe film against the drum, each driven through its contactwith the filmon the drum, there often is a tendency for that part of the film betweenthe two rolls on the drum to become enlarged or too full so that thefilm fails snugly to hug the drum. Thus with an arrangement of drum andlight beam as illustrated results not only in a lack of uniformity ofi'llm movement through the light beam but it also affects the focus ofthe beam on the sound record. I overcome the above mentioneddifficulties and objections by causing the pressure roll 9 to be drivenby means other than the film on the drum in such a manner that there isa tendency for the roll to overdrive the film, that is to move the filmslightly faster than it is moved by the drum. Various means may beprovided for so driving the pressure roll. In Fig. 2, Where I haveillustrated by way of example a simple and effective means for thispurpose, the arm 40 which is pivotally -of the two rolls 9 and 44 beingcorneal. That portion of the drum face which engages roll 44' is, inFig. 2, the same diameter as those portions supporting the film adjacentthe sound record. Preferably the roll 9 has a tire of soft, resilientmaterial such as felt or rubber and the roll 44 has a hard faceadaptedto resist wear. In Fig. 2 I have shown the diameter of ,the drumslightly reduced (the -showing being considerably exagi gerated) atthose portions thereof which contact with those parts'of the lm removedfrom the sound track in order to insure the most intimate contactbetween film and drum adjacent the sound track. Arm 40 supporting therolls 9 and 44 and also arm 38 supporting the pressureguide roll 7 areyieldingly held against the drum. For the best operation I prefer thatthe respective pressures exerted by the rolls at the beginning and theend of the film-wrap about che drum shall always have a predeterminedrelation with each other andin order to insure this relation I employthe single coil spring 46 which connects at its ends 105 with the twoarms and at an intermediate point passes over the stud 47. Because ofthe difference in diameters of rolls 9 and 44, roll 9 tends to move thefilm faster than it is moved by the drum but since the diameter andcoefficient of friction of 110 the roll 9 is greater than. that of roll44 slipping occurs only between roll 44 and the drum. By this means itwill be seenthat the film is constantly urged forward and is therebycaused rmly to hug the drum. It should be understood 115 that thetendency of the roll 9 to move the iilm forward is never so great thatthe film is caused to slide forward on the drum. In Fig. 3 I haveillustrated a modification in which the rolls 50 and 51 correspondingrespec- 120 tively to rolls '9 and 44 both are cylindrical and vthatportion of the drum engaging roll 51 is somewhat larger in diameter thanthe film supporting portion. In this figure the drum is shown having auniform diameter of its filmengaging face. The construction andoperation otherwise is like that of the form shown in Fig. 2.

If desired the nlm-engaging roll may be arranged so that it contactswith the lm only at one side of the sound track and in the case of arecorder where there is no necessity for the light to pass through thefilm the drum may be constructed to support the film for the entirewidth of the latter. Under certain conditions the roll 7 may be raisedout of actual contact with the iilm on the drum in which case it-functions only as a guide for the film approaching the In the drawing Ihave purposely omitted for the sake of greater clearness a complete-showing of the enclosing casing of the apparatus, the light 140 source,the driving means for the sprocket and drum, etc. as such form no partof my present invention and are well known to those familiar withapparatus of this character.

What I claim as new and desire to secure by 145 Letters Patent of theUnited States, is:

1. In apparatus for recording sound on a nlm and for reproducing soundfrom a record film including a sprocket and/a drum arranged to engage afilm at spaced points thereof, means for et, including a brake and acontrolling member therefor movable in response to changes in the lengthof the film between the sprocket and drum and having a mass operative tomaintain the controlling member in contact with thev lm and to controlthe pressure applied by the brake, the mass of said member serving torender the brake substantially unresponsive to sudden small variationsin the speed of the film,

2. In apparatus for recording sound on a hn and for reproducing soundfrom a record ilm including a sprocket and a drum arranged to engage aiilm at spaced points thereof, a compensator for regulating the speed ofthe drum including a controlling lever therefor carrying a roll arrangedin a loop in the lm between the sprocket and drum and a brake operatedby said lever, said lever having a mass secured thereto and arranged tomove the lever in response to gradual variations in size of the loop,said lever by virtue of the inertia of said mass being substantiallyunresponsive to sudden small variation in illm loop size. t

3. In apparatus for recording sound on a film or for reproducing soundfrom a record film including a uniformly driven drum about which the lmis wrapped and means for increasing the adhesion of the film and drumcomprising tensioning means for the lm approaching the drum, and anover-driven member arranged to4 press the lm against the drum Where itleaves the same.

4. Film driving mechanism including a drum about which the lm is adaptedto be Wrapped,

means for rotating the drum ata uniform speed, and means ten n' g tooverdrive the'film on the drum comprising a rotatable member having oneportion engaging said drum .and another portion arranged to press thenlm against the drum.

5. Film driving mechanism including a drum about which the ilm isadapted to be wrapped, means for rotating the drum at a uniform speed,

and means tending to overdrive the lm on the drum comprising a rotatablemember having one portion driven by the drum and another portionengaging the lm on the d'rum and a pivotal support for said memberintermediate said portions.

6. Film driving mechanism including a drum about which the film isadapted to be Wrapped, means for rotating the drum at a uniform speed,and means tending to overdrive the film on the drum comprising arotatable member having one portion driven by the drum and anotherportion engaging the iilm on the drum, and means for resilientlymovingthe rotatable member toward the drum including a pivotal support for themember arranged between said portions.

7. Film driving mechanism including a druml about which the lm isadapted to be wrapped, means for rotating the`drum at a uniform speed,and means tending to overdrive the i'llm on the drum comprising a shafthaving at one end a roll engaging said drum and at the other end a rollarranged to engagethe film on the drum, an intermediate bearing for theshaft having a pivotal mounting perpendicular thereto and a springactuated arm supporting said mounting.

CHARLES L. HEISLER.

CERTIFICATE 0F CORECTION.

l Patent No. l, 920, 789.

August l, 1933.

` CHARLES L. prisma.

it is hereby certified that error appears in the printed specificationof the above. numbered patent requiring correction as follows: Page 3,lines 27 and 28,

- claim 3, strike out the word "including" and insert a comma; and 4thatthe said l with this correction therein that the same may LettersvPatent should be read Signed (Seal) Patent Office.

ll.. J. Moore. Acting Commissioner of Patente.

